Sending a message to the entire domain did not send to computers on a different subnet, why?

Group Net Send can only broadcast net send command to other computers using the same domain, on the same subnet. Only users on the local subnet that belong to the specified domain, receive the message. For additional information, view the article in the Microsoft Knowledge Base. Basically, NetBIOS over TCP/IP uses b-node broadcasts for name resolution and registration on your local LAN segment. If you want your router to forward b-node broadcasts, you must enable UDP ports 137 and 138.

Our Group Net Send product simply wraps the features of the Messenger Service of Windows into a handy, easy to use application. Click here to read more detailed information about how the Messenger Service of Windows interacts with NetBIOS over TCP/IP Name Resolution and WINS.

The "domain" alias specifies the set of computers that have the same domain name defined as their domain or as their workgroup and listen to broadcasts on the same subnet. For NetBIOS over TCP/IP, specifying the "domain" alias can also succeed across subnets if the domain name is resolved by a name server, or if NetBIOS datagram broadcasts are forwarded across routers. Therefore, messages sent to a domain do not have guaranteed delivery to all members of the domain. It is also possible for some domain members to receive the message multiple times if they have multiple transports installed that support NetBIOS.